<!--
  例子
 -->

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <span v-if="isUser">
      <label for="username">用户账号</label>
      <input type="text" id='username' placeholder="用户账户">
    </span>

    <span v-else>
      <label for="email">用户邮箱</label>
      <input type="text" id='email' placeholder="用户邮箱">
    </span>

    <button @click='isUser = !isUser'>切换类型</button>
  </div>

  <script src='../../js/vue.js'></script>
  <script>
    new Vue({
      el: '#app',
      data: {
        isUser: true
      }
    })
  </script>
</body>
</html>